A delineation of the complete linear amino acid sequence of T2-phage induced deoxycytidylate deaminase is planned. As a starting point, the S-cyanoethylated subunit of the enzyme (ca. 20,000 molecular weight) will be cleaved by cyanogen bromide to yield two peptides (CNBr-1 and CNBr-2) which are separable on Biogel P-30 chromatography. CNBr-1, which is the larger of the two peptides and is derived from the amino end of the protein, will be alkylated at its lysyl residues with citraconic or maleic anhydride. Subsequent treatement of this peptide with trypsin should result in hydrolysis at its four arginine residues to yield 4 to 5 peptides. CNBr-2, when treated similarly, should yield 2 to 3 peptides at most. Isolation of the tryptic peptides can be affected by gel-exclusion, ion-exchange, paper chromatography, or a combination of these methods. The purified peptides will be sequenced by both automatic and manual procedures. To obtain overlap-peptides for placement of the above tryptic peptides in their appropriate order in the protein, CNBr-1 and -2 will be split at their tryptophanyl residues with BNPS-skatole. Additional overlap peptides, if necessary, will be obtained with thermolysin or chymotrypsin. An attempt will also be made to determine the amino acid sequence at the substate and allosteric effector sites by using derivatives of substrate and effector which can be fixed to this site. A comparative analysis with deoxycytidylate deaminases from animal sources (rabbit, monkey, and human liver) purified to homogeneity by an affinity column technique will be made. Antibody to the animal enzyme will be used to determine if a radioimmune assay can be developed to diagnose specific pathologies associated with the elevation of this enzyme in serum.